Comparing logic-based and XML-based rights expression languages

Several rights expression languages (RELs) have been proposed to describe licenses governing the terms and conditions of content access. In this field XrML and ODRL play a prominent role. Both languages are powerful yet complex. In this paper we propose a way of analysing RELs and we apply it to ODRL, XrML and to LicenseScript, a REL we propose. In addition, we test these languages against a number of example scenarios. These examples bring new insights, and shed new light on some of the limits of XrML and ODRL